Process for recovering metals from their ores



Patented Mar. 28,

2 SHEETS--SHEET l- Mxed sul-#Mov nowsuide are copper ore Coarse cvushin fine 'fir-din '1 'hnwer soR ha culed residual Wash: qases APPLICATION FILAED 1uvNE11, 1919.

Yy-f.

E. S. LEAVER AND C. E. VAN BARNEVELD.

PROCESS FOR RECOVERING METALS FROM THEIR ORES.

Ho+ qqs Iron pyfites Hirt` Calc'mes W f2 f ATTORNEY..

E. S. LEAVER AND C. E. VAN BARNEVELD.

PROCESS FOR RECOVERING METALS-FROM THEIR DRES.

Hok qases con'lrainnq Solvo 191mm voasler or oLher source APPLICATION FILED lLlNE ll, 1919. I

Patented Mar. 28, w22.

2 SHEETS-SHEET 2.

Mlxed sull'mle Y non-sul-Fide eoppe ore O *f weder Het Pulp conlanlnq 50i-soluble minerals iJCSSuxlf-zld'esJ und cleansed. sulfids Blower cells or 1kan ks to remave traces of S02 amd lm oxdze sullwl'es Melcxlll'c irgn from dean zer or ofhev souree Tube mlll wl'h iron balls breakinq up cemernl copper und pvecpH-a-l'inq copper remoim'nq n soLuHon Pulp aorrkunnq cernercopper, any melullic copper Fr'um ultimesl ond any cleansed suldes to buld up copper perL-ewlaqe V Concen-l-foLl-es l conlannq preeiprolleol or meullizeol coppew` and cmy cleansed sull-des TmlS NUR-sul'lllde Copper ove (wil-h or wlhoml suHde) m acid copper-bemin bulli up by elrculal-on o Qrindinq'in pebble mm solulon pr eq nani solution Residual Copper sulwliun velurned +0 pebble mill ElecJrrolyl-lc cop-per Charles E vana rneveld BY www fw# ATTORNEYS.

EDMUND S. LEA'VER AND CHARLES E. VAN BARNEVELD, 0F TUCSON, .A RIZOll'..v

PROCESS FOR RECOYERING METALS FRUM THEIR GRES.

To all it. may concern."

Be it known that We, EDMUND S. LEAVER and CHARLES E. VAN BARNEVELD, citizens of `from ores or metallurgical products.v The invention is applicable particularly to the recovery of metals from oxidized or nonsulide ores, but it may also be used with mixed or complex ores containing both sultide and non-sulfide constituents and, in such case, it provides for effective recovery, for

example, of the values from mixed ores containing copper in both sulfide and non-sul-A fide form.` It is also applicable to the recovery of zinc-in the non-sulde form and of manganese in the formof higher oxides.

Our invention is based primarily on the use -of sulfur dioxide, together with water, as a leaching agent on non-sulfide ores, such as oxidized copper ores. Leaching of oxidized copper ores by means of a sulfur dioxide solutionhas been proposed but has generally been carried out in such manner as to involve the production of acid sulfites by maintaining sulfur dioxide in excess during the leachin operation and subsequent precipitationA o the copper as suliitesl by driving off the excess of sulfur dioxide.l

This method of operation, While apparently simple, has not resulted in successful commercial operation, notwithstanding large expenditure of time, money and eiiiort by many met'allurgists. The process is, moreover, open to the objection that the metal is recovered in sulfite `form.

The main object of the present invention is to utilize sulfur dioxide as a leaching agent in such manner as to provide a practical commercially operative process capable of successful operation on a large scale and applicable to wholly` oxidized ores or to the ores containing both oxidized (or other nonsulfide) and sulfide constituents, and capable'of recovering the values in metallic form, from the non-sulfide constituents. The term non-sulfide ore is here used as covering any ore except the sulfide ores, and applies especially to oxide (or oxidized) ore,carbonates, silicates, and also native copper.

According to the present invention, sulfurA Specicatin of'Letters Patent.

Application led .Tune 11,

Patented Mar. 28, i922.

i919'. serial n; 303,419.

dioxide is applied -to the ore, together with water, and with oxygen in such manner that the copper is brought into solution eventually in the form of a sulfate, such sulfate being then treated for precipitation for the recovery -of metallic copper therefrom. In carrying out the process, the sulfur dioxide is supplied as a constituent'.V of hot gases containing oxygen and passed in countercurrent to a pulp consisting of the ore, to-

gether with water, or solution, in such manturned to the counter-'current cycle.. By this.

operation the maximum eiiiciency of solution is attained and the sulfur dioxide' is e'ectively utilized with minimum waste.

Another object of the invention is to provide, in some cases, for utilization of pyritic 'ore as a source of a sulfur dioxide as used in the process, and also of the meta lic iron required for the precipitation of the copper. In the accompanying drawings, F ig. 1 is a longitudinal sectlon. Y

F ig. 2 is a transverse section of an apparatus carrying out the leaching operation above described. V

Fig. .2a is an enlarged section of the pulp outlet and gas inlet for the apparatus.

Fig. 3 is a flow sheet showing one method of applying the" invention tothe recovery of gases contalnmg oxygen,

copper from mixed sulfide and non-sulfide ores in such mannerthat the copper is recoverediby precipitation from clear solution. Fig. 4f is a flow sheet similar to Fig. 3, except thatthe copper is recovered by precipitation followed by flotation.

Fig. 5 is a liow sheet for a rocess wherein the metal is recoveredV by e ectrolytic precipitation.

The apparatus shown in Figs. 1 and 2 com-` prises a drum l mounted on bearings 2, provided with driving means 3 to rotate slowly,

with means 4 to feed ore pulp into it at one end, and with -means 5 to discharge the leached pulp at the opposite or exit end, which exit end is also the point .of entry oit the gas carrying'sulfur dioxide andoxygen, so as to cause said gases to pass in reverse direction or counter-current to the movement of the ore pulp therein. The said gases may be supplied from a roaster 6@ The interior of the drum 4 is divided into compartments 7 by a series of transverse partitions 8, each of which is provided with a plurality of openings 9 through which the ore pulp may-pass through the successive compartments7 to the end or discharge compartment 10. Longitudinal bars or baffles 11 and buckets or lifters 12 are provided in each compartment 7 and lifters-or buckets 13 are provided in compartment 10. The ore pulp is fed into the first compartment 7 drops to the bottom of said compartment; the buckets or lifters 12 in their ascending movement caused by the rotation of the drum raise the or@J pulp until it is spilled on the horizontal bars 11 below in such manner that the ore pulp is splashed and distributed over the surfaces of the bars and against the transverse partitions 8 in fine descending drops and particles, thereby insuring 1nt1- mate and prolonged contact between the oreV particles and the counter-current sulfurous and oxidizing gases. With a constant feed of ore pulpl into the drum 1, a iow is established within the drum so that the pulp is gradually passed through the successive compartments 7 into the last or discharging compartment 10, the lifters 18 of which raise the pulp and drop it into the discharge or exit pipe 5 whereby it is conducted through trap opening 14 to discharge launder 15.v

Aopposite end hot, and la counter-current flow is developed which results in'the lpulp becoming progressively warmer and the gas becoming correspondingly colder until the pulp at the discharge end is heated to any desired temperature.

We have discovered.- that when SO2 is introducedl as a hot dilute gas containing less than 4 per centr SO2 by volume (the balance ofthe gas being largely air, which has lost a portion of its oxygen, and which may contain the -various impurities commonly found in roaster gases) and isp'rojected into a ne spray of hot pulp or solution that the-absorption of SO2 is practically negligible and that these hot pulps or solutions will contain practically no free SO2 and will discharge from the drum as practically neutral pulp or solution. We have determined by experimental work on a'100 ton scale that the approximate temperatures necessary to edect this expulsion of SO2 vary for different. strengths of SO2 as follows: 350 C. or over for a gas carrying lper cent SO2; 45o C. or over' for a gas carrying 2 per cent SO2; 50 C. or over for a gas carrying 3 per cent SO2. The absorption of 2 is progressively greater as it comes in contact with the `colder pulp, and the presence of a large excess of other gases limits the absorption to a small fraction of the SO2 absorbing power of cold water. "Furthermore, any free SO2 in solution is expelled as the pulps become heated in their travel towards the discharge end. Free acid will attack iron; therefore,

to reduce the consumption'of iron in the precipitation of copper from sulfate solutions the pulp discharge from the drum must be practically neutral. This is an additional reason for maintaining certain temperature of solution in the drum near the discharge end. Y v

The operating conditions of the drum may be summarized as follows Sucient SO2 must be introduced to ei'ect rapid solution and at the same time 'sufficient oxygen must be present to effect the rapid oxidation of sulfites to sulfates. Sufficient sulfur (in whatever form) must be burned to heat the gas to the' point which will produce the desired terminal pulp temperatures. The density of the ore pulp will be one limiting .factor in the capacity of the drum since 3 per cent appears to be the desirable maximum SO2 content of the gas if good oxidationis to be effected. Thus for each particular case, there is a proper relation between pulp density, admission temperature of gas', dilution of gas and leaching may readily be made in each case from a Y eiciency, which will determine the quantity .of pyrite to be burned. Approximations knowledge of -the conditions; subsequent regulation of thevariable conditions is a simple matter; from this, the'requirements may be accurately determined and positively maintained It maybe assumed that very seldom will a greater dilution than one and one-half parts of water to one part of ore be `necessary to obtain the proper conditions for contents.- The pyrite requirement at thisv plant is approximately 3 tons of iron pyrite containing 40 per cent sulfur in order to raise the temperature of the pulp from 26o C. admission temperature to 46 C. at the exit, delivering a 2 per cent SO2 gas.

The above described process results in the production of a solution of copper sulfate mixed with the pulp residue. In order. to recover the copper from this solution various methods may be adopted according to the particular conditions of the ore and other factors relating to the expense of such recovery. Some of the methods of operation lare illustrated in the flow sheets on the accompanying drawings, it being understood that these flow sheets pre-suppose the Apresence of sulfide, as well as non-sulfide, ore in the material being treated, and in case sulfide ores are absent, the steps of fiotation, etc., appropriate to the separation thereof, will be omitted.

Fig. 1 is a flow sheet for the process involving recovery of copper from clear sulfate solution,- afterthe latter has been separated from the exhausted pulp by decantation or filtration. In case sulfides are absent from the ore, the first flotation indicated may be omitted as shown by the dotted line leading from the fine grindingv to the tails, The pulp passing from the leaching drum above described is filtered or decanted, for example, by counter-current decantation in suitable apparatus 20, to produce'a clear solution of copper sulfate. This solution is then passed to suitable blower cells or tanks 21, wherein air is blown through it, with the result that any remaining SO2 is completely expelled. The solution then passes to precipitating tanks or cells 22,l preferably arranged for countercurrent operation. In general, metallic iron is the most suitable precipitant, and, in

many cases, it is desirable to provide for production of such iron adjacent to the e'xtracting plant, to avoid the expense of importing the same.

This flow sheet also illustrates a preferred method of obtaining at one operation the sulfurl dioxide required for theextraction above described and metallic (sponge) iron for precipitation of the copper from the clear solution.

Tron pyrites, with or without auxiliary minerals, such as chalcopyrite, is crushed and roasted in roaster 19 (producing gases containing SO, and- O) and the hot calcines, which may contain copper as well as iron are passed to'a suitable deoxidizing apparatus wherein the iron (and also the copper present, if any) are reduced to metallic condition, preferably in such manner that the iron is in the form of sponge iron. This deoxidizing' operation may be performed in any suitable apparatus 23 adapted to subjectthe roasted ore to the action of a reducing agent, such as a reducing gas (for example',

iron in the ore to be reduced to the required 7 iron,A the temperature being insufficiently high to fuse the iron so reduced. The gases produced in the roasting operation'and containing sulfur dioxide and oxygen l are assed, while still hot, into the extracting rum 1 to effect the leaching operation above described. The metallic iron produced in the deoxidizingapparatus is passed to the precipitating apparatus 22, which may be of any suitable type, and may comprise a series of agitating or pulping tanks 25, alternating with lsettling tanks 26, whereby the iron is presented successively to stronger or more pregnant solutions, and the barren or waste solution is drawn off' at oneend of the series and the cement copper at the other end. This cement copper also contains the residue from the calcines (including the gold, silver and copper in the original pyrites), and may be smelted or treated in apparatus 30, in the usual manner for production of the metal or -metals in desired form. As indicated at 27, f

the apparatus 23, for example, scrap iron may be used, if available.

other suitable manner,

IeXtent, to the condition of metallic sponge In some cases there may be sufficient sulfur dioxide-in the stack gases from the smelter 30 to enable the sameJ to be used asa source of sulfur dioxide, as indicated by the connection 31 from the smelter 30 back to the gas intake of the extracting drum 1.

In case it is desirable 'to prevent any possible detrimental effect from the escape into the atmosphere of the S02 in the gas discharged from the extracting `or lixiviation drum 1; or in case it is desired to utilize the full effect of all the S02 generated; or in case longer contact is desiredJ between the reagent and the mineral; a tower 33, or other system, may be introduced into which the gas as it leaves the lixiviation barrel is conducted, either with the pulpor counter current to the pulp (or part of the pulp), a preliminary pulp discharge .from this preliminary leach would then be fed direct into the SO2 lixiviation drum.

Another method of recovering SO2 from the gas as discharged from the drum would be by condensation, as would be effected, for instance, ina drip-towel, with or without the use of steam as a collector. The resulting condensed S02 solution would then be introduced into the pulp-intake-end of the SG, lixiviation drum.

In some cases mechanical methods, such as leach being thus effected.- The gravit concentration, or dotation, may be copper as Well as the sulfide copper and in that case the operations may follow the-flow sheet .of Fig. 4. In connection With recovery by flotation, the cleaning of the sulfide copper by the action ofthe leaching solution in the lixiviation drum 1 is of advantage in enabling cleaner and more elicient Hotation.

It will be understood that the flotation (or the gravity concentration, as the case/may be) may beeli'ected inany suitable manner by any of theusual flotation apparatus, or by the use of tables, vanners, etc., as the case maybe, and that in this case, as in Fig. 3, the sulfur dioxide for extraction with other iron for precipitation may be furnished either from the pyrites roasting and deoxidizing apparatus 19 and 23, or from any other sultable sources. l

`In the' case there is any conslderable lamount ofsulfide present in the pulp' (for.

example, by reason of failure of the preliminary flotation in a flotation apparatus 38, before the lixiviating operation, to eff solution passing from the lixiviating drum 1, the flow sheet shown in Fig. 5 may be folloWed-this flow sheet indicating the ordinary method of cyclic operation with solution followedby the electrolysis and return of the relatively barren solution to the leaching apparatus, with the exception that the leaching in this case is primarily by SO2 solution, followedby oxidationto produce copper sulfate solution. This process has 'the special advantage over the usual sulfuric acid leach, in this connection, that the-presence of SOZserVeS tokeep the iron in ferrous condition, eliminating the necessity of spe.-

cial reducing tower.

In some cases, the-'copper may be precipitated from the sulfate solution by the action of sulfur dioxide under pressure and heat (with or Without neutralization with lime), so as to precipitate metallic copper. Or, if

desired, the copper may be precipitated as sulfide, by H28- for example, and the sulufide then treated in any suitable manner for lproduction of the metal.

What we claim is: 1. The process Whichconsists in treating pulp containingva non-sulfide ore-material,

togetherwith Water,l to the action of hot gases containing sulfur dioxide and oxygen, to produce metallic sulfate in solution, precipitating the metal from such sulfate by a precipitating agent and separating the metal so precipitated.

2. In the recover of metallic'values from ore containing sul de and non-sulfide constituents, the process Which consists in treating a pulp containing such constituents to the action of hot gases including sulfur dioxide and oxygen, to produce metallic sulfate in solution and to remove oxidizedy material from the sulfide constituents, precipitating thel metal from such solution by the' action of a precipitating agent, separating such metal and also separating from the pulp the sulfide-constituent thereof.

3. A process, accordin to claim 2,.in which a part of the sul de constituent is separated from the pulp by concentrating operation before treatment with sulfur dioxide and oxygen,- and residual sulfide is separated from the pulp by concentrating operation after treatment with sulfur dioxide and oxygen. p

4. In the recovery of metallic values from ores, the step which consists in passing pulp comprising divided non-sulfide ore" material and -water in counter-current with hot` gases containing sulfur dioxide and oxygen to cause the sulfur dioxide to be first absorbed by the water, converting the non-sulfide metal values in the pulp to the form of sulfte and oxidizing the sulfite .to sulfate by the action of the oxygen and of the heat of the gases, and the excess sulfur dioxide being expelled from the Water as the latter becomes heated by the gases so as to pass back into the .stream of gases passing in countercurrent t'o the cold pulp so as to cause such sulfur dioxide to be re-absorbed in such cold pulp.

In testimony whereof We have hereunto subscribed our naines this 29th day of May,

EDMUND S. LEAVER. .CHARLES E. VAN BARNEVELD. 

